The present invention relates to a method and apparatus for producing an element-free gap or a so-called space section in a continuous length slide fastener chain composed of a carrier tape and a row of discrete elements securely fastened to the carrier tape along one longitudinal edge peripherally around a stringer core reinforcing the tape edge as well as for removing some additional number of elements at the end of the element row of a slide fastener chain when cut in a product length, the elements being formed by die-casting a metal or injection-molding a synthetic plastic resin.
It is a usual practice nowadays of manufacturers of slide fasteners that, instead of manufacturing slide fasteners of individual product lengths as such, a continuous length slide fastener chain is first manufactured by securely fastening fastener elements, which have been shaped by die-casting a metal or injection-molding a plastic resin, on to the stringer core reinforcing the peripheral edge of the carrier tape to form an element row and then to form so-called space sections free of the elements by removing several elements at certain intervals followed by cutting the carrier tape within the space sections into the individual desired product lengths. Further there may often be a necessity to remove several of the fastener elements from a slide fastener of a finished product length to obtain a shortened slide fastener, for example, in tailors and other users as well as in a retailor's shop according to customer's order to match the slide fastener to the design or size of clothes or other products to which the slide fastener is to be sewn.
There have heretofore been proposed various methods and related apparatuses for the production of space sections in a continuous length slide fastener chain of the above type with the above-described purpose. One of the methods known in the art is concerned with cutting the coupling head portions of the elements only off the fastener chain within the desired section and thereafter removing the leg portions of the elements left in engagement with the stringer core off the carrier tape by pulling. Another method comprises the steps of pressing fastener elements in a space length as desired into deformed, flattened configuration and thereafter forcibly separating the thus deformed elements from the stringer core. These prior art methods, however, suffer from the drawbacks that the carrier tape or, especially, the stringer core is sometimes injured as well as that the removal of the fastener elements is sometimes incomplete because the methods involve the step of forcible plucking of the deformed elements or element debris from the stringer core.
In order to mitigate the above-described drawbacks in the prior art methods, an improved method and an apparatus have been proposed in U.S. Pat. No. 3,958,319, in which the fastener element is cut at the head portion thereof in the direction toward the stringer core and divided into two pieces readily removable by knocking off the stringer core. This method and the apparatus therefor, however, also cannot be free from certain problems to be improved as described below.
Namely, the cutter punch for cutting the fastener elements at the head portions thereof must be provided with a plurality of cutter blades at regular intervals corresponding to the pitch and the number of the elements to be removed within the range of the desired space length and, in addition, chain support members must be provided at the position between each pair of the adjacent cutter blades in order to grip and hold the stringer core in the knocking of the divided elements off the stringer core. Moreover, bifurcated spacer arms must be provided below the cutting punch to fix the elements at the position so as to facilitate cutting of the elements at the head portions thereof. Therefore, disadvantages are brought about by the necessity that the cutting punch, the chain support members and the spacer arms must have each an appropriate shape and size in accordance with the size and pitch of the fastener elements to be removed so that a set of these tools suitable for a fastener chain must be replaced with another set for working with another fastener chain having elements of different size and pitch.
Besides, the apparatus as a whole is relatively large so that inconvenience is unavoidable in handling the apparatus for the work of shortening slide fastener chains, for example, in a retailer's shop.